By passing an undirected magnetic field through the wall of a pipe or conduit, the magnetic field is largely attenuated by the distance traveled and due to its natural field shape, and by eddy current losses that can occur in electrically or magnetically conductive materials that make up the wall of the pipe or conduit, or are proximate to the wall of the fluid carrying conduit, and in the armatures themselves. This attenuation limits the magnitude of the force and power available to vibrate the immersed vibrating element in high viscosity fluids such as hydraulic-fracturing fluids (“fracking fluids”), oil well cementing fluids, for example in the thick walled high pressure conduits which are common in the hydraulic-fracturing and oil well drilling industries.
In addition, magnetic particles (e.g., rust particles or iron filings) in a fluid stream are often attracted to and adhere to the electromagnetic drivers and sensors. These entrapped particles cause measurement errors for the immersed vibrating element type meter because of the added weight, magnetic permeability, electrical conductivity, and damping properties of the adherent particles.